The ATGO ECM Code Page will help you find the problem associated with your ECM Trouble Codes. Check your Trouble Codes using the instructions below and then compair the code to the correct chart below.

ECM Codes

Turn ignition switch to OFF position

Locate Data Link Connector (DLC), see image below.

Jumper the A&B terminals(a paper clip or a jumper wire work ok)

Turn Ignition switch to ON position.

Count the flashes on the "CHECK ENGINE" or "SERVICE ENGINE" light.

FLASH, pause, FLASH, FLASH = code 12

To clear all codes from your ECM, disconnect the negative battery cable at the battery and wait about 30 seconds then reconnect it. If your cars stereo requires you to enter a 4 digit code when you do this, the best thing for you to do is to just remove the fuse going to the ECM.

Oxygen sensor voltage stays between 0.35 and 0.55 volts for 3 seconds during closed loop operation and will set code after 40 seconds for Century and Cutlass Ciera. For the Lumina, the oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds during closed loop operation and will set code after 2 minutes. Both systems can go into open loop after 15 seconds.

Coolant temperature sensor signal indicates a temperature colder than -22° F after the engine has been running for 2 minutes.

21

TPS voltage was above 2.5 volts for 2 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more under 1800 RPM.

22

TPS voltage was under 0.2 volts for 2 seconds when the engine was running.

23

Inlet ATS signal showed an air temperature of -22° F after the engine has been running for 1 minute.

24

TPS signal was less than 2% with engine speed between 1400 and 4400 RPM and the MAP signal showed low voltage and high manifold vacuum. Transmission was not in park or neutral.

25

Inlet ATS signal showed an air temperature over 275° F for more than 2 seconds after the engine has been running for 5 minutes and vehicle speed was greater than 44 MPH.

32

EGR open command did not change the fuel mixture when the command was given during off idle operation. EGR opening should cause the mixture to be slightly richer because of the low oxygen content of exhaust gas.

33

MAP sensor signal voltage was too high (low vacuum) for at least 5 seconds when throttle opening was under 2%.

34

MAP sensor signal voltage was too low (high vacuum) when engine speed was under 1200 RPM or when engine speed was over 1200 RPM with throttle opening was over 20%.

35

Idle speed was over 150 RPM outside the desired engine speed commanded by the ECM.

42

The EST signal did not change when the ECM applied bypass voltage to the ignition module.

Oxygen sensor voltage was above specification. Century and Cutlass Ciera was over 0.75 volts for 50 seconds in a closed loop. Lumina was over 0.7 volts for 30 seconds and throttle angle was between 3% and 45%.

51

PROM error.

53

Charging system voltage was greater than 16.9 volts for more than 50 seconds. Repair charging system.

Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds. Engine was at normal operating temperature and had been running for at least 2 minutes after start with a throttle angle above 5%.

MAP sensor signal voltage was too high (low vacuum) for 5 seconds when throttle opening was under 4%.

34

MAP sensor signal voltage was too low (high vacuum) when engine speed was under 1200 RPM or the engine speed was over 1200 RPM with a throttle position angle above 21%.

42

The EST signal did not change when the ECM applied bypass voltage to the ignition module.

43

The ECM did not detect a knock signal during near wide open throttle operation with coolant temperature above 194° F or the knock signal was present for 5 seconds or more during normal engine operation.

Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds. Engine was at normal operating temperature and had been running for at least 2 minutes after start with a throttle angle above 5%.

Coolant temperature sensor signal indicates a temperature colder than -27° F for 30 seconds after the engine has been running for at least 30 seconds.

21

TPS voltage was above 2.5 volts for 8 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more.

22

TPS voltage was under 0.2 volts for when the engine was running.

23

Inlet air temperature sensor signal showed an air temperature below -22° F after the engine has been running for 5 minutes.

24

When engine speed was between 1200 and 4400 RPM and throttle position angle was less than 3%, the MAP signal showed low voltage (high manifold vacuum) for at least 5 seconds.

25

Inlet air temperature sensor signal showed an air temperature over 302° F after the engine has been running for 5 minutes. On Brougham models the inlet air temperature sensor signal shows a temperature above 297° F with an engine speed greater than 35 MPH.

32

EGR open command did not change the MAP sensor signal. Normal EGR flow should cause slight decrease in manifold vacuum which would change MAP sensor signal.

33

MAP sensor signal voltage was too high (low vacuum) for 5 seconds when throttle opening was under 4%.

The EST signal did not change when the ECM applied bypass voltage to the ignition module.

43

The ECM did not detect a knock signal during near wide open throttle operation with coolant temperature above 194° F or the knock signal was present for 4 seconds or more during normal engine operation.

44

Oxygen sensor voltage was under 0.25 volts for 50 seconds of closed loop operation. On Brougham models the oxygen sensor voltage was under 0.2 volts.

45

Oxygen sensor voltage was over 0.75 volts for 30 seconds with a throttle angle above 20%. On Brougham models the oxygen sensor voltage was over 0.7 volts.

51

PROM error.

54

Fuel pump voltage was not present at fuel pump sense line for 2 seconds after the ECM has sent the fuel pump on command.

Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds. Engine was at normal operating temperature and had been running for at least 2 minutes after start with a throttle angle above 5%.

High battery voltage OR Direct inition system open or shorted to ground

17

RPM signal problem

21

TPS voltage was above 2.5 volts for 3 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more, or TPS was above 4.8 volts at anytime.

22

TPS voltage was under 0.2 volts for 2 seconds when the engine was running.

23

Manifold air temperature sensor signal showed an air temperature below 22° F after the engine has been running for 5 minutes.

24

When engine speed was between 1400 and 3600 RPM and throttle position angle was less than 2% for at least 4 seconds.

25

Manifold air temperature sensor signal showed an air temperature over 302° F for 2 seconds after the engine has been running for 2 minutes and vehicle speed was greater than 5 MPH.

26

Fault in quad driver module

27

Fault in 2nd gear switch

28

Fault in 3rd gear switch

29

Fault in 4th gear switch

30

N/A

31

Low voltage at manifold absolute pressure sensor OR Fuel injector OR Park or neutral switch OR CAM diagnostic OR Governor malfunction OR Wastegate overboost OR Wastegate eletrical signal open or shorted to ground

32

EGR open command did not change the fuel mixture when the command was given during off idle operation. EGR opening should cause the mixture to be slightly richer because of the low oxygen content of exhaust gas.

33

MAP sensor signal voltage was too high (low vacuum)

34

MAP sensor signal voltage was too low (high vacuum)

35

Idle speed can not be set to desired RPM

36

Burn off at mass air flow sensor OR Problem in transmission shift OR Fault in direct ignition system OR Missing pulses in electronic spark timing signal

37

N/A

38

Fault in torque converter clutch brake switch

39

Fault in torque converter clutch circuit

40

N/A

41

Fault at cam sensor OR Cylinder select error OR Tach input error

42

Fault at electronic spark timing circuit OR Fault at direct ignition system OR Fault at fuel cutoff relay circuit